sbin/hammer/misc.c

   1 /*
   2  * Copyright (c) 2008 The DragonFly Project.  All rights reserved.
   3  *
   4  * This code is derived from software contributed to The DragonFly Project
   5  * by Matthew Dillon <dillon@backplane.com>
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  *
  11  * 1. Redistributions of source code must retain the above copyright
  12  *    notice, this list of conditions and the following disclaimer.
  13  * 2. Redistributions in binary form must reproduce the above copyright
  14  *    notice, this list of conditions and the following disclaimer in
  15  *    the documentation and/or other materials provided with the
  16  *    distribution.
  17  * 3. Neither the name of The DragonFly Project nor the names of its
  18  *    contributors may be used to endorse or promote products derived
  19  *    from this software without specific, prior written permission.
  20  *
  21  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  22  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  23  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  24  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
  25  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  26  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
  27  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  28  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  29  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  30  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  31  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  *
  34  * $DragonFly: src/sbin/hammer/misc.c,v 1.2 2008/01/21 00:03:31 dillon Exp $
  35  */
  36
  37 #include "hammer.h"
  38
  39 /*
  40  * (taken from /usr/src/sys/vfs/hammer/hammer_btree.c)
  41  *
  42  * Compare two B-Tree elements, return -N, 0, or +N (e.g. similar to strcmp).
  43  *
  44  * Note that for this particular function a return value of -1, 0, or +1
  45  * can denote a match if delete_tid is otherwise discounted.  A delete_tid
  46  * of zero is considered to be 'infinity' in comparisons.
  47  *
  48  * See also hammer_rec_rb_compare() and hammer_rec_cmp() in hammer_object.c.
  49  */
  50 int
  51 hammer_btree_cmp(hammer_base_elm_t key1, hammer_base_elm_t key2)
  52 {
  53         if (key1->obj_id < key2->obj_id)
  54                 return(-4);
  55         if (key1->obj_id > key2->obj_id)
  56                 return(4);
  57
  58         if (key1->rec_type < key2->rec_type)
  59                 return(-3);
  60         if (key1->rec_type > key2->rec_type)
  61                 return(3);
  62
  63         if (key1->key < key2->key)
  64                 return(-2);
  65         if (key1->key > key2->key)
  66                 return(2);
  67
  68         /*
  69          * A delete_tid of zero indicates a record which has not been
  70          * deleted yet and must be considered to have a value of positive
  71          * infinity.
  72          */
  73         if (key1->delete_tid == 0) {
  74                 if (key2->delete_tid == 0)
  75                         return(0);
  76                 return(1);
  77         }
  78         if (key2->delete_tid == 0)
  79                 return(-1);
  80         if (key1->delete_tid < key2->delete_tid)
  81                 return(-1);
  82         if (key1->delete_tid > key2->delete_tid)
  83                 return(1);
  84         return(0);
  85 }
  86